1. Field of the Invention
The present invention relates generally to communications networks having nodes which undergo dynamically changing topology, such as in mobile radio networks. Specifically, the invention pertains to an architecture and node structure in which nodes are grouped into physical or local area subnets, and each node of each physical subnet is affiliated with a corresponding node of each of the other physical subnets thus forming a number of regional virtual subnets.
2. Description of the Known Art
Mobile radio networks are expected to play an important role in future commercial and military applications, especially when a wired backbone network does not exist. Such networks are suitable when an instant infrastructure is needed and no central system administration (e.g., a cellular system base station) is available.
A peer-to-peer mobile radio network is a collection of mobile packet radio nodes that create a network on demand and without administrative support, and which nodes may communicate with each other via intermediate nodes in a multi-hop mode. Thus, every network node is also a potential router. Typical applications for peer-to-peer networks include mobile computing in remote areas, tactical communications, law enforcement operations and disaster recovery situations. A critical issue in these networks is their ability to adapt well to dynamic topology changes caused by movement of member nodes relative to other nodes of the network. Adaptation to topology changes requires changes both in channel assignment and in routing.
Mobile radio networks have existed since the 1970's. At first, these networks aimed at providing classic data services such as file transfer. Recently, there has been a growing interest in rapidly deployable and dynamically reconfigurable wireless networks, for supporting multimedia traffic including voice and video information as well as data. Several important networking issues need to be resolved for these networks to support multimedia services. Carrying real-time voice and video information imposes stringent time delay constraints on the networks. Multimedia networks must possess high performance and reliability in the nature of high throughput and fault tolerance, and low delay.
Prior work on mobile radio networks with dynamically changing topology, concentrated primarily on channel access and routing schemes in arbitrary physical topologies. See, e.g., E. M. Gafni et al., Distributed algorithms for generating loop free routes in networks with frequently changing topology, IEEE Transactions on Communications, COM-29:11-18 (1981). To improve network performance and reliability, several methods of topology control have been proposed involving adjustment of transmission ranges. See T. C. Hou et al., Transmission range control in multihop packet radio networks, IEEE Transactions on Communications, COM-34(1) (January 1986); and L. Hu, Topology control for multihop packet radio networks, IEEE Transactions on Communications, 41(10) (October 1993). More recently, a multi-cluster architecture for multi-hop mobile radio networks supporting multimedia traffic has been proposed. M. Gerla et al., Multicluster, mobile, multimedia radio networks, Wireless Networks, 1(3) (October 1995).
As far as is known, no architecture or configuration suitable for mobile radio networks has been proposed that incorporates network partitioning, and, further, is adaptable to dynamic topology changes due to node mobility.